1. Field of the Invention
The invention relates in general to an optical drive, and more particularly to a position detecting device of an optical drive for detecting whether a tray for supporting a disk has reached a playing position and thus timely enabling a control circuit of the optical drive.
2. Description of the Related Art
Because an optical drive rotates an optical disk at a high speed, the optical drive has to be opened for the ejection of the disk in a safe state in order to ensure the operation safety of the user. Meanwhile, the optical drive has to correctly judge that the optical disk has been positioned and then rotate the optical disk for the precise read and write operations to prevent the optical disk from being damaged.
FIG. 1 is a schematic illustration showing an interior structure of a conventional optical drive 1. The conventional optical drive 1 accommodates a tray 3 in a hollow casing 2. The tray 3 supports an optical disk 4 and may slide into or out of (tray-in or tray-out) the optical drive 1 from an opening at one end of the casing 2 freely. A spindle motor 5 for clamping and rotating the optical disk 4 is disposed at a middle of the tray 3. A pick-up head 6 capable of sliding back and forth in a radial direction of the optical disk 4 is disposed on the optical disk 4 to read the data on the optical disk 4. A servo circuit board 7 is disposed at a bottom of the tray 3 to control the spindle motor 5 and the pick-up head 6. The rear end of the servo circuit board 7 is connected to one end of a flexible cable 8. The other end of the flexible cable 8 is connected to a mainboard 9 at a rear end of the casing 2. A CPU (Central Processing Unit) 10 for processing a data signal, and a limit switch 11 are disposed on the mainboard 9. A projection 12 projecting from the bottom of the tray 3 presses against the limit switch 11. An ejecting mechanism 13 is disposed at the rear end of the tray 3, and a rotatable latch part 14 is disposed at a lower edge near the front end of the tray 3. One end of the latch part 14 is connected to an actuator 15, and the other end of the latch part 14 is formed with a hook 16 for hooking a fixing part 17 projecting from the casing 2. A panel 18 is disposed at the front end of the tray 3 to shield the front end of the casing 2. An ejecting button 19 is disposed on the panel 18.
When the ejecting button 19 is pressed, the CPU 10 controls the actuator 15 to rotate the latch part 14 such that the hook 16 releases the fixing part 17 and the ejecting mechanism 13 pushes the tray 3 out of the casing 2. Meanwhile, the projection 12 on the bottom of the tray 3 leaves the casing 2 and enables the limit switch 11 to make the CPU 10 brake the spindle motor 5. Thus, the optical disk 4 stops rotating and the optical drive shuts down. On the contrary, when the user wants to push the tray 3 supporting the optical disk 4 into the casing 2, the latch part 14 resists against the ejecting mechanism 13 to hook the fixing part 17 under the pushing force of the user as the tray 3 is moved into the optical drive. Meanwhile, the projection 12 at the bottom of the tray 3 again triggers the limit switch 11 as the tray 3 is moved in, such that the CPU 10 knows that the tray 3 has been positioned to start the optical drive.
However, the conventional optical drive 1 uses the limit switch 11 disposed on the mainboard 9 to detect the position of the tray 3 such that the CPU 10 starts or shuts down the optical drive 1 and controls the rotation of the optical disk to prevent the consumer from danger, prevent the optical disk from being damaged and ensure the precise access of the optical drive 1. Under the requirements of the miniaturized product and the low cost, the limit switch 11 occupies a portion of the area of the mainboard 9 such that the effective circuit layout area of the mainboard 9 is reduced. Meanwhile, the component cost and the manufacturing complexity of the optical drive are increased. Thus, the conventional structure of the optical drive still has to be simplified.